months. They are also particularly sensitive to other adverse conditions
such as drying and reduced pH.
The principal environmental reservoir of pathogenic campylobacters
is the alimentary tract of wild and domesticated animals and birds and it
is a commonly found commensal of rodents, dogs, cats, dairy cattle,
sheep, pigs, poultry and wild birds. The high optimum growth temper-
ature ofC. jejuniandC. colicould be an adaptation to the higher body
temperature of birds and reflect their importance as a primary reservoir
of the organism. Asymptomatic human carriage also occurs.
Though they would not appear to survive particularly well outside an
animal host, campylobacters can be commonly isolated from surface water.
Survival is enhanced by low temperatures and studies conducted in Norway
have shown that strains ofC. jejuni,C. coliandC. laridisremained viable in
unchlorinated tap water at 4 1 C for 15 days (10 days at 12 1 C) and 10–15
days in polluted river water at the same temperature (6–12 days at 12 1 C).
Under adverse environmental conditions campylobacters have been
reported to adopt a ‘viable non-culturable’ state where the organism
cannot be isolated by cultural methods but nevertheless remains infec-
tive. Evidence for this is conflicting, one study has shown that viable non-
culturableC. jejunican revert to a culturable state by passage through an
animal host but others have failed to observe this effect.
Studies in the United States and Europe have isolated Arcobacter
species from pork and poultry meat, though the rates of isolation vary
widely (0.5 to 97%). Physiologically,Arcobacterspecies differ signifi-
cantly fromCampylobacterandHelicobacterin being both aerotolerant
and capable of growth at 15 1 C, attributes which could give them a
considerable advantage when it comes to foodborne transmission. How-
ever the evidence for an association betweenArcobacterand diarrhoeal
disease in humans remains circumstantial at present.
7.4.3 Pathogenesis and Clinical Features
Enteropathogenic campylobacters cause an acute enterocolitis which, in
the absence of microbiological evidence, is not easily distinguished from
illness caused by other pathogens. The incubation period is from 1 to 11
days, most commonly 3–5 days, with malaise, fever, severe abdominal
pain and diarrhoea as the main symptoms. The diarrhoea produces
stools containing 10^6 –10^9 cells g^1 , which are often foul-smelling and can
vary from being profuse and watery to bloody and dysenteric. Gastro-
intestinal symptoms are sometimes preceded by a prodromal stage of
fever, headache and malaise which lasts about a day. The diarrhoea is
self-limiting and persists for up to a week, although mild relapses often
occur. Excretion of the organism continues for up to 2–3 weeks. Vom-
iting is a less common feature.
194 Bacterial Agents of Foodborne Illness